Use of adipic acid as a tableting lubricant



United States Patent 3,506,756 USE OF ADIPIC ACID AS A TABLETING LUBRICANT George Carr Hoss, Elkhart, Ind., assignor to Miles Laboratories, Inc., Elkhart, Ind., a corporation of Indiana No Drawing. Filed July 7, 1969, Ser. No. 839,714

Int. Cl. A61j 3/10 US. Cl. 424-44 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to a tableting lubricant which can be mixed with a powdered tabletable composition to aid during the compression thereof into tablets, and particularly, to the use of adipic acid as a lubricant.

Tableting lubricants perform the general functions of providing (1) surface lubrication for the punch and die surfaces which come into contact with one another and with the compressed composition and (2) internal compression lubrication in order to lend pliability to the composition being compressed. Both of these lubrication functions must be satisfied if the powdered tabletable composition of interest is to be tableted commercially on tableting machines operated at high speeds. Some prior lubricants have provided only one of these two necessary lubrication functions and hence have necessitated joint use with another lubricant. A general problem with these prior lubricants has been their insolubility. This causes a tablet formed from an otherwise soluble composition to exhibit the appearance of a clouded suspension rather than a clear solution when dissolved in water. Talc and magnesium stearate are examples of such lubricants. Other lubricants are precluded in one or more marketing areas because of their toxicity. Examples of such lubricants are boric acid, benzoic acid and polyethylene glycol. Some tableting lubricants such as sodium benzoate have therapeutic action and therefore alter the pharmacological acceptability of tablets in which they are included.

SUMMARY OF THE INVENTION The adipic acid tableting lubricant can be used with a wide range of powdered tabletable compositions to allow high speed tableting thereof. While various amounts of adipic acid can be mixed with such compositions depending upon the presence therein of ingredients which impart some lubrication and upon the tableting speed desired, it is usually sufiicient to use about at least adipic acid based on the total weight of the composition being tableted when no other lubricants are used. If desired, adipic acid may be used in larger amounts, approaching the total tablet weight, since it is cohesive when compressed.

Adipic acid exists naturally as minute, colorless, monoclinic prisms which permit use according to the present invention without further modification. If desired, these small prisms can be comminuted to any desired fineness. Mesh sizes of 40 and finer are particularly preferred for 3,506,756 Patented Apr. 14, 1970 use with most powdered compositions. Adipic acid is characterized by its low toxicity and hence it may be used for tablets which are intended to be taken internally.

The tabletable compositions which can be lubricated for tableting with adipic acid can, for example, be any compositions which are cohesive enough when compressed to form and retain a tablet shape. Such compositions can be composed of powdered detergents, disinfectants, germicides and/or abrasives which disintegrate when placed in water to form cleaning solutions of various types. Inclusion of quarternary compounds, such as cetyl pyridinium chloride, is particularly useful when cleaning tab lets are to be produced.

The preferred compositions, however, are effervescent mixtures comprised of an alkali metal carbonate or bicarbonate and an acid such as malic, citric or tartaric acids which are capable of rapidly releasing carbon dioxide upon addition of water thereto. When the carbon dioxide has been released, the solution formed is useful for its alkalizing properties when taken orally.

The compositions can also include at least one therapeutic agent, water-soluble excipients, and any necessary coloring or flavoring agents, diluents, binders, or disintegrators. In such compositions the therapeutic agent may be acetylsalicylic acid, acetyl p-aminophenol or other suitable analgesic.

If necessary, binders may be added to the base composition to promote cohesion. All of such compositions are tabletable in that they are cohesive when compressed. However, without a lubricant most of such compositions can be tableted only by hand, since they cause binding and scoring of the punches and dies of power driven tableting machines. In order to attain commercial production speeds a tableting lubricant must be employed to reduce surface friction and internal compression friction.

The adipic acid of the present invention may be used as the sole lubricant or may be employed in conjunction with another lubricant included in the tabletable composition. More particularly the adipic acid lubricant can be substituted for various materials which function as tablet lubricants during compression.

In effervescent tablets adipic acid provides the additional effect of taking part in the effervescent action. When the adipic acid does form part of the effervescent couple it is neutralized to a metal salt, if a sufiicient amount of an alkaline material is employed, and in such form is even more highly soluble than is the free adipic acid. Hence, when greater solubility than that for free adipic acid is desired, a source of alkali metal ions may be included in the pharmaceutical composition, whereby upon dissolution of the composition in water the alkali metal salt of adipic acid is formed and any solubility limitations of adipic acid are obviated. Generally, however, this is not necessary due to the fact that the adipic acid is used in amounts low enough so that the volume of water normally used for dissolution of the tablets is suflicient to dissolve all of the adipic acid employed.

Amounts of at least about 5% adipic acid based on the total weight of the lubricated tabletable composition are generally sufiicient to allow high speed tableting when adipic acid is used as the sole lubricant. When it is used as one of at least two tableting lubricants a proportionately smaller amount may be used. Amounts of about from 5% to 15% adipic acid allow tableting of effervescent mixtures at rates up to about 5000 tablets per minute on rotary tablet machines containing 47 punch and die sets. Each punch and die set produces approximately 106 tablets per minute in such machines. On a rotary machine containing 33 punch and die sets, tablets may be compressed at a rate of 76 tablets per minute per set for a total production of about 2500 tablets per minute.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the following example the concentrations of components are stated as weight percent of the weight of lubricated composition as tableted.

Component Amount, grams Sodium bicarbonate 1674 Citric acid (anhydrous) 1000 Adipic acid 320 Calcium hydrogen orthophosphate 205 Magnesium oxide 4 Sodium cyclohexylsulfamate 20 Sodium saccharinate 2 Peppermint oil encapsulated in gum acacia 16 The above components in the amounts stated were dried, reduced to 30 mesh screen size and thoroughly mixed. The adipic acid in the composition was present in a concentration of 9.8 weight percent.

The resulting mixture was placed in a hopper of a hand-operated punch rotary tableting machine from which the mixture was fed to the dies of the punch and die sets of the machine. The compression pressure was 11 kg. The tablets produced were 0.158 in. thick and Weighed approximately 3.2 g. each.

Upon completion of the run the tablets were found to be smooth surfaced and elegant in appearance. Upon immersing in 120 ml. of water at 25 C. a tablet quickly etfervesced and dissolved to give a sparkling clear solution of pH 5.8 with no sediment.

What is claimed is:

1. A tablet producing a clear aqueous solution and being free from insoluble tablet lubricants or other tablet excipients or components which cause a tablet formed from an otherwise soluble composition to produce a clouded suspension having undesirable surface scum rather than a uniform solution when dissolved in'water consisting essentially of a compressed, essentially freeflowing mixture of a powdered, Water-soluble, tabletable essential active ingredient and, as the essential tablet lubricant, a dry-mixable tableting lubricant comprising adipic acid.

2. The tablet of claim 1 wherein said powdered, watersoluble, tabletable essential active ingredient is an internal use oral therapeutic agent, effervescent couple alkalizer, quaternary ammonium disinfectant or solution-forming, external use, solid surface general cleansing germicide.

3. The tablet of claim 2 wherein said effervescent couple alkalizer is an adipic acid-free effervescent mixture of a base and an acid.

4. The tablet of claim 1 wherein said adipic acid is present in an amount of at least about 5% based on the total tablet weight.

5. The tablet of claim 3 including an additional therapeutic agent.

6. The tablet of claim 4 wherein said powdered, watersoluble, tabletable essential active ingredient is an adipic acid-free eifervescent mixture of a base and an acid.

References Cited UNITED STATES PATENTS 2,448,524 9/1948 Gentner 117-100 2,971,848 2/1961 Polya 99-141 2,977,300 3/ 1961 Bergen et al. 252-18 2,977,301 3/ 1961 Bergen et al. 252-1.8 3,105,792 10/1'963 White 42444 3,136,692 6/ 1964 Bandelin 42444 3,355,392 11/ 1 967 Cantor et a1. 252 99 FOREIGN PATENTS 1,074,958 2/ 1960 Germany. 1,075,255 2/ 1960 Germany.

845,628 8/ 1960 Great Britain.

SHEP K. ROSE, Primary Examiner U.S. Cl. X.R. 

